1. Field of the Invention
The present invention relates to a self-diagnostic system for determining maintenance conditions of lubricants in oil-utilizing machines operating under intermittent loads. More particularly, the present invention relates to a system and method for determining the condition of oil in an engine, transmission, or the like, in order to optimize oil maintenance intervals.
2. State of the Art
Lubricating oils are typically comprised of high molecular-weight products of the petroleum distillation process. The base constituents of these oils are typically hydrocarbon chains having anywhere from 16 to 30 carbon atoms, and a boiling point higher than 350xc2x0 C. Undesired constituents such as tars, asphalts, greases, and paraffin waxes are preferably removed during the refining process, and certain additives such as thickening agents, detergents, and anti-oxidants may be added to impart desired properties to the oil.
As oil is used in the high temperature, high stress environment of an internal combustion engine or other oil-utilizing machine, the base hydrocarbons tend to break down over time. Typically, the relatively long hydrocarbon chains of the base oil break up and degrade into oxidized forms of hydrocarbons such as polyacohols, aldehydes, carboxylic acids, esters, etc., which have inadequate or undesirable properties. When some significant proportion of the base oil has broken down in this way, the oil will no longer protect the machine from damage as desired.
At present, oil changes in internal combustion engines and similar oil-utilizing machines are typically performed according to the mileage or hours of operation of the machine, not according to the directly identified needs given by the chemical state of the lubricating oil. However, it will be appreciated that the miles driven or hours of use do not necessarily indicate the condition of the oil. For example, operation under heavy or rapidly varying loads, or under dusty or extreme temperature conditions will tend to cause oil to break down sooner than otherwise. A mileage or time-based schedule is thus only an approximation of the actual needs, based on numerous assumptions. The result is that the lubricating oil may be changed too infrequently, resulting in accumulated damage to the mechanical parts, or it may be changed more often than needed, causing needless maintenance expense and producing excessive waste oil. While one could periodically remove a sample of oil from a vehicle""s oil reservoir and have it chemically tested, this is so time consuming, expensive, and inconvenient as to be essentially impractical.
It would be desirable to have a self-diagnostic system that could sense the actual chemical condition of the lubricating oil in intermittently operated machines, and provide an operator or maintenance person with an indication when the oil has reached a certain point of chemical degradation.
It is therefore an object of the present invention to provide a system for detecting the chemical condition of lubricating oil within the oil reservoir of an intermittently operating machine, such as an internal combustion engine, in order to determine the maintenance needs of the lubricant.
It is another object of the invention to provide an informational display indication that will notify a user when the lubricating oil is degraded beyond a specified point, to thus allow prompt replacement of the oil.
It is another object of the invention to provide a system for detecting the condition of lubricating oil within the oil reservoir of an internal combustion engine by a sampling/analysis sequence which is initiated when the engine is switched off and which sequence continues during engine cool-down.
It is yet another object of the invention to provide a system for sensing the composition of vapors in the head space of an oil reservoir where most sensor data acquisition occurs during the period when the engine is not in operation.
The above and other objects are realized in a system and method for determining the condition of oil in an oil-utilization mechanism which has an oil reservoir having a head space above the oil, said system comprising: a sensor means for sensing the composition of vapor in the head space and for developing a signal representing said composition; a processor for receiving the signal and for determining if the signal corresponds to predetermined parameters; and apparatus for producing a discernable indication if the processor determines that the signal deviates from the predetermined parameters.
In accordance with one aspect of the invention, a system for sensing the composition of vapors within an oil reservoir of an internal combustion engine initiates a sampling/analysis sequence when the engine is switched off, which sequence continues during engine cool-down.
In accordance with another aspect of the invention, a sample of oil is removed from the oil reservoir of a continuously running machine and deposited in a holding reservoir. A sampling/analysis sequence of the vapors within a head space of the holding reservoir is initiated when the oil sample is placed in the holding reservoir, and continues as the oil sample cools down.
Other objects and features of the present invention will be apparent to those skilled in the art, based on the following description, taken in combination with the accompanying drawings.